taste-motion

Motion's job is to explain the interface, not decorate it. Every animation must answer: what happened, where is it, what do I do next.

1. THE DURATION SCALE (Fixed Tokens)

Under 100ms reads as a blink (unless it's a snap, which brutalist packs do deliberately). Over 900ms reads as a slow website.

2. THE EASING TOKENS (Fixed)

• Standard (UI states): cubic-bezier(0.4, 0, 0.2, 1) — fast in, calm out. Default for hovers and toggles.
• Emphasized (entrances/reveals): cubic-bezier(0.22, 1, 0.36, 1) — long calm tail. Premium feel.
• Exit: cubic-bezier(0.4, 0, 1, 1) or faster — exits are snappier than entrances.
• Spring/overshoot (playful packs only): cubic-bezier(0.34, 1.56, 0.64, 1) — max once per element, never on loops.
• Never use ease-in-out as a catch-all. Never use linear except for marquees/progress.

3. WHAT TO ANIMATE (And What Not To)

Animate: transform and opacity. That's it. 60fps guaranteed.

Never animate: width/height (layout jank — use transform: scale), margin, top/left (use transform), box-shadow at large sizes (use a pre-blurred pseudo-element), filter: blur on large surfaces.

4. CHOREOGRAPHY (Entrances)

• One scene per section: on scroll reveal, the section's elements enter in 2–3 stages (heading → body → CTA), 60–120ms apart, same duration and easing. Stagger is hierarchy.
• Distance ≤ 20px for reveals (translateY 8–16px) + opacity. Bigger distances look like PowerPoint.
• Scale entrances ≤ 0.96→1 and only on dialogs/popovers, never on full sections.
• Hero: one sequence, 600–900ms total, elements entering once. No looping float, no repeating wave.
• Loop allowance: exactly one class of loops allowed per page — ambient status indicators (live dots, loaders, spinners). Everything else loops = error.

5. MICRO-INTERACTIONS (Hover, Press, Focus)

• Hover: 100–150ms, standard easing, one property change (bg tone, border, translateY −1 to −3px). Never both color AND position AND shadow at once.
• Pressed: inverse of hover (translate down, shadow off), 80–120ms.
• Focus-visible: 2px ring, 3:1 contrast, outline-offset: 2px, animated in with 100ms fade — never outline: none without replacement.
• Disabled: no hover states at all — the element must look inert (opacity 0.4–0.5, no pointer change).
• Transitions on load/state-change only where the state is visible; a transition nobody can perceive is dead code.

6. SCROLL & LAYOUT

• Scroll-triggered: IntersectionObserver (or CSS animation-timeline where supported), one reveal per element, then done. No elements that re-animate on every scroll pass.
• Sticky: allowed for nav and section labels; sticky + animation = performance risk, keep the animation out.
• View transitions / page transitions: 300–500ms, shared-element moves where they earn it (list → detail). Disabled entirely under prefers-reduced-motion.
• Layout transitions: FLIP pattern (transform-based), never re-layout animations.

7. REDUCED MOTION (Non-Negotiable)

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

• Above the CSS gate, zero motion by default when the media query matches: no parallax, no auto-scroll carousels, no marquees.
• Animate presence only: content appears without motion (opacity 0→1 over 1 frame).

8. CHECKLIST (Fail the Page If…)

• Any element animates for more than ~1.5s (outside loops/loaders).
• More than one looping element per viewport.
• Any width, height, margin, or top animation.
• Reveal distances beyond 20px.
• ease-in-out used as the global easing.
• Every element on the page animates on load (bounce-entrance festival).
• No prefers-reduced-motion handling exists at all.

If you can't explain an animation in one sentence, delete it.